Gauging device for large parabolic antennas



Aug. 9, 1966 J. F. BELL 3,264,743

GAUGING DEVICE FOR LARGE PARABOLIC ANTENNAS Aug. 9, 1966 J, F, BELL 3,264,743

GAUGING DEVICE FOR LARGE PARABOLIC ANTENNAS Filed June 8, 1964 3 Sheets-Sheet 2 Allg- 9 1955 J. F. BELL GAUGING DEVICE FOR LARGE PARABOLIC ANTENNAS Filed .June e, 1964 3 Sheets-Sheet 5 United States Patent Office 9, 6,

3,264,743 GAUGING DEVICE FR LARGE PARABULIC ANTENNAS Joseph F. Bell, Elmhurst, Ill., assignor to Andrew Corporation, ()rland Park, Ill., a corporation of Illinois Filed June 8, 1964, Ser. No. 373,318 4 Claims. (El. S23-174) The invention relates to a gauging device for curved surfaces, and more particularly to a gauging tool or instrument for use in adjusting a curved surface contour, such as that of the parabolic dish of a large directional antenna.

As the electronic communications arts have pushed toward greater and .greater sensitivity and directionality of antenna systems, larger and larger structures have been employed for the parabolic reflectors used for high signal gain. As is Well known in the electronic (and optical) arts, the narrowness of the concentration of an electromagnetic energy beam, i.e., the directional gain, may be accomplished by increase of the aperture or parabolic arc of the reflector. Accordingly, larger and larger parabolic dishes have been, and are being, used.

The full benefit of increase of reflector size is obtainable only by the highest of precision in maintaining the exact desired shape of the reliector. Because the increase in aperture represents an increase in distance of the peripheral portion from the feed (which term of course includes use in reception) at the focus, extremely precise preservation of the exact desired curvature is required in this region. When a reflector is constructed of aperture dimension-s comp-arable to the dimensions of a large building, the establishment and preservation of a surface shaping or contour which is of the required curvature in all regions becomes difficult. The reflector surface construction virtually universally employed is a skin of conducting mesh, supported on an appropriate backing framework. Since it is a virtual impossibility to construct the framework in such a manner that the requisite accuracy of shaping can be done by relying solely on the framework for definition of the shape, it has been found framework, thus permitting the formation of the requisite exact curvature.

The present invention lies in a tool or gauge which is suitable for u-se in making the adjustments just mentioned, inl installing the skin upon its supporting framework to produce the exact contour desired, without introducing a vast amount of complex measuring and calculation, but without imposing prohibitive costs (or perhaps sheer impossibility) on the construction of the gauging equipment.

A more or less conventional way of inspection or measurement of a curved surface with Iregard to conformity to a standard is the use of a template. A block or sheet of wood or metal may be formed with an edge or surface of the desired shape and laid on the surface to be inspected or adjusted, with exactness of conformity being visually observed at each point. Such a use of a template is essentially impossible when dealing with structures such as the 60footdiameter reflector for use with which the embodiment of the invention later to be described is designed. It is unnecessary to point out in detail the problems of both fabrication and use of such a template, in monitoring the exact curvature of a structure of the size just mentioned.

The size of reflector 4here involved accordingly cannot employ the tools and methods which are conventional in measuring the surface shape in smaller structures. One possible solution to the problem, of course, is the pointby-point measurement of slope with respect to reference vertical and horizontal directions, but the making of such measurements is extremely diicult, particularly where the skin is to be adjusted upon a completely erected framework, i.e., in its use orientation.

It is accordingly the object of the present invention to provide a relatively simple type of gauging device or tool which is capable of being used in a manner which is reasonably comparable with the manner in which a template block or sheet is used with smaller reflector constructions. In general, this object has been accomplished by providing a gauging device or instrument having certain features of both its construction and its manner of operation resembling that of the usual template, but with important differences which will be seen. The present invention may perhaps be best understood by considering it as a device which in essence converts a curved contour, which is in itself very difficult to inspect visually for error, to a linear or planar contour, the inspection of which for accuracy is a well-known simple routine operation in structure of large size, such as walls of buildings, etc.

This conversion is made by mounting a support member in a reference orientation extending across the region whose curvature is to be monitored, the support member bearing feelers spaced along the curved surface and urged into Contact therewith, each feeler being associated with a position-indicator (its outer end in the simplest and most desirable embodiment), all the indicators being in alignment when the predetermined correct curvature exists in 4the surface upon which the feelers rest. With this construction, it is unnecessary to attempt to provide such a prohibitive structure as (for example) an exactly shaped prefabricated template. The alignment (or misalignment) may readily be observed with a simple optical instrument such as a transit or telescope, and, by provision of suitable calibration markings on the indicators, the degree of misalignment, and the required amount of adjustment for alignment, may readily be determined and communicated to the person making the adjustments.

The broad principle of construction just described is, in accordance with the further teachings of the invention, implemented in a relatively simple and inexpensive manner, but without loss of accuracy, in the embodiment to be described, which accordingly incorporates the further Vteachings of the invention which may best be understood from consideration of the various features of its construction, best described by reference to the attached drawing, in which:

FIGURE 1 is a side view in elevation showing the overall construction of a gauging tool or instrument ernploying both the broader and narrower aspects of the features of novelty of the invention, along with the dotted indication of a parabolic reflector construction with which it is designed to be used;

FIGURE 2 is a View in front elevation of the device of FIGURE l;

FIGURE 3 is a fragmentary enlarged view of a portion of a mounting assembly, constituting a portion of the device, employed for rotational mounting of one part of the tool or instrument at the center of a reflector;

i FIGURE 4 is a sectional view taken along the line 4-4 of FIGURE 3, in the direction indicated therein by arrows, and also showing the end of a shaft constituting a portion of the device, omitted in FIGURE 3 for clarity of illustration;

FIGURE 5 is a fragmentary sectional view illustrating the mounting of the opposite, or front, end of the central shaft of the device;

FIGURE 6` is' an enlarged view of a feeler and indicator rod and its support and mounting, constituting a portion of the device, and shown partially in elevation and partially in section; and

FIGURE 7 is a Iview inside elevation of the assembly of FIGURE 6.

As seenA in FIGURES 1 and 2, a contourrgauge madev in accordance with `the invention, gener-ally indicated by the numeral 20, is shown as it is employed in the adjustment of the precise surface contour of a parabolic reflectorfgenerally indicated by .the numeral 21 and .shown The ygauge 20V has a shaft 28 which is supported in av first bearing generally indicated at 30, at the center of lthe dish or reflector structure, yand a second beaning generally indicated at 32, which is held centered on the axis by wires or similar mooring means 33 extending out to the framework. V

Mounted on the shaft is a gauging assembly framework 314, which isl counterbalanoed by a oounterweitght framework 36, bearing a counterweight 38. TheV gauging assembly framework 34 bears gauging rod assemblies 40a, 40b, etc., which are radially spaced along the framework or anni 34, and vextend in :parallel fashion tocontactthe skin 22. The framework 34 consists in general of an outer radial portion 41, and an inner radial portion 41a, the latter being formed of slightly angularly related individual lengths to form an overall more or less curved member roughly approximating the curved shape of the rellector. 'I'his entire assembly is rigidiz/ed by cross braces 42 and diagonal braces 43 (only examples of these being illustl'ated), and tie-wires 44 are suitably tightened on the main framework and on transverse tiebars 45.l Further, suitable tie-wires 46 connect portions of the gauging assembly framework or arm 34 with the countenweitght framework 36. 1 for olanity.)

As will be readily understood, the bracing and rigidiz'ing of the movable assembly is sho-wn only suggestively in the drawing, which omits not only much of the structure.

employed for this purpose, but also the turnbuckles and similaradjustment means employed in the formation yof the overall highly rigid, countenbalanced, and properly oriented rotatable assembly mounted on the'shaft 28. The manner of mounting the shaft 28 at the inner bean` Ving 30 is shown in FIGURES 3 and 4. A mounting plateL 48hasreinforced radial extensions 49 forming a spider adapted for rigid mounting yat the center of the Ldistro-1 rellector. As will readily be understood by those skilled= the plate 48.` The blocks 52 have radial threaded. ape-rf tures 54 receiving adjusting boltsy 56 which extendin through the blocks 52. The inner end of each bolt 56 is annulanly grooved at 58, and is capped by a dog 60, having a well-bore 62 seating the rounded extreme encl64 of th bolt 56. The dogs 60 rare secured in placef'bypins 66 driven through suitable apertures therein and seating in the grooves 58;

'The inner surface 68 Vof each dog 60is a conical seg-Y ment, f thus. forming in essence .a rearwardly facing ,ad-y

justable conical seat. A mating conical surface. ,70` is formed on `a plug 72 welded intothe ,end ofthe tubular shaft 28.= The. outerend ,of this plug has mutually perpendicular .transverse bores 74 and 76 permitting rota.

tion by insertion of a suitable rod.

The reflector 211 has a (All tie-Wires are omitted from FIGURE 28 is secured to an internal plug 78 by bolts 80. The: plug 78 is formed with a shoulder yat 82 andthe frontend portion 84 extendingtherefrom is rotatable ini a bearing sleeve 86 which extends thro-ugha boss 88 welded to a heavy plate 90. The plate, 90 is suitably apertured for the securing of the supports 3-3` which maintain its centered relation, as previously described. v A washer 92 i-s secured by Va bolt 94 and lock-washer 96to the outer end of the portie-n.84 within the bearing 86thus completing ,the .outer end of the rotatable assembly.

FIGURE `6 shows the .construction and mounting of one of the gauging rods40,'all of which are essentially identical except yfor lbodynlength. The body' is formed from a tubular rod` 98. Thisfis mounted in suitable apertures in an outer slide bracket v and an `inner lslide bracket 102; :secured to suitable mounting plates 104 and 106, respectively, these latter being mountedon the re-fV spective outerand inner portions 41? and 41a' ofthe frame-z (As indicatedin .the drawing, the plate 106 is v ,by'a pin 116 driven through the tube, bears on one endl ofa coiled compressionspring 118,'Y the other end of` which bears on the bracket;00. The spring 1h8 thus urges the rod inwardly toward contact with the curved surface under measurement. .Alfurther.rfpini120, near the opposite bracket 102,;` acts asa limit stop for thismotion under the urging of the spring 118.

To the lowerV end of the tube 98 isweld'ed a base 122v having :an -ear extension v124 apertured at 126,` to receive a reduced portion 1128 of a stud 130,-having a head 132 serving to mount a nylon wheel 134 journalled on: a suitable bearing liner 136. This assembly; is held in place by a nut 138 :threadedvonto the end 140 of the stud 130.

The wheel 134 is formed with a relatively tine or thin edge .142,:and the rotational position or orientation isi maintained by a guide rod 144 which slides in a guide aperture 1461inthe bracket :102 andis securedto the base 122. of the rod assembly by a pin 148.l

The pin 144 maintains the rotational axisofthe wheel 134 vat all times ,-radial,iand the .relativelyjne edge or; support surface of the;'wheelf134 assures that the -longitudinaltpositioning'ofthe rod under lthe urging of the.- spring 118 is determined solely bythe position ofthe sur-a face against which thespring .urges the wheel, and is free of error produced by slope or pitch. It will ,be seen upon v study thattthe useof a wide contact l.surface .on the edge Vof the wheel 134 -would introducefan Verror in thecor-` .responderme between longitudinal rod positionand exact` locationfof the point of the surface under measurementA in Valignment -with the center of the rod.;V The mounting f l means'for the wheel, previously described, aligns the contact point of' the. wheel-with thexrod, as seen in FIG- URES 6 and 7,' and the'narrowpointof contact prevents;

the radial pitch lor slope .from affecting the :accuracy'of the lndication given by the longitudinal rod position.

In thel outer end of each tubular rod 98 is a calibration plugv 150,' with scribed markings 152, preferably at equal fractional parts',Y of an inch yfrom the end.154`..Y The .end

ofthe tubular rod 98 is'slotted atz156anda clamp v158 1s used to tighten thesliding :lit of the plug.V 150, after exactiadjustment to the -desiredoverall length.

The lengths of therod assemblies, ,as grossly con-LV structed and asnally adjusted by ther positioning ofthe calibration plugsjust described, may beset by calculation so that the successive .differentials in length, zas a function of radial distance from they axis, formthe exact parabolic the surface underlying a given angular position of the gauging tool is exactly of the shape desired. Any deviation from the desired curve appears as a deviation from straight-line orientation, and the amount of required adjustment of the region of contact of any given rod may be determined merely by observation of the number of divisions or markings by which that rod fails to be in the proper alignment. The use of a transit or similar sighting device permits ready observation and communication of the required adjustments.

It will of course be obvious that many variants of the particular construction illustrated may be employed without departure from the teachings of the invention. Furthermore, a variety of dimensions, materials, etc., may be used. The selection of materials, dimensions, etc., will `of course vary greatly with both the details of construction of the gauging devi-ce and with the size and desired accuracy of the surface to be adjusted or otherwise measured or observed in this manner. The particular embodiment shown in the drawing is one which has been very successfully employed for th'e contouring of the reflecting surface of a parabolic reflector of 60-foot diameter. In this particular construction, the gauging arm was formed of a plurality of longitudinal sections bolted together by use of suitable anges (not illustrated) provided for this purpose, in order to permit ready transportation and assembly and disassembly, the required 30foot radius of the gauging arm being formed of a plurality of pieces each less than eight feet long. In this particular construction, there was employed a shaft of 8inch diameter aluminum tubing of a length of approximately fifteen feet, and aluminum was also used in the form of angle and similar stock in the framework. The adjustability provided by the calibrating plugs permits eld assembly and resetting to exact dimensioning after bolting together of the frame and rigidizing by the guys, etc.

As earlier indicated, persons skilled in the art will readily devise many forms of the invention, some of which will readily be obvious while others will become apparent only after study. Accordingly, the scope of the protection to be afforded the invention should not be limited to the particular embodiment illustrated and described, but should extend to all utilizations of the teachings of the invention as defined in the appended claims, :and equivalents thereof.

What is claimed is:

1. A surface contour gauge for use in shaping large parobolic antenna reflector comprising:

(a) a rigid rotatable support,

(b) .a first bearing lat the inner end of the support adapted to be mounted at the center of the rellector :and a second bearing at the outer end of the support having laterally adjustable mounting means for aligning the support for rotation about the parabolic axis,

(c) .a radial arm on the support,

(d) parallel gauging rods spaced along the arm and spring-urged inwardly in the axial direction, the lengths thereof decreasing substantially parabolically with radial distance from the axis,

(e) and substantially identical sets of longitudinally spaced markings on the outer ends of the rods,

whereby conformity of the reflector to the parabolic contour may be observed by viewing of the alignment of the outer end portions of the rods, and the amount of required adjustment of the surface a-t any point is indicated by the measure of misalignment provided by the markings.

2. The gauge of claim 1 having wheels on the inner ends of the rods mounted on radial axes of rotation directly aligned with the rods.

3. The gauge of claim 2 having the markings on longitudinally adjustable end portions of the rods.

. 4. The gauge of claim 3 having a counterweight opposite the arm.

References Cited by the Examiner UNITED STATES PATENTS 223,372 l/l880 Miner 33-174 1,093,867 4/1914 Legare 33-174 1,364,534 l/192l Walter 33--175 2,172,368 9/1939 Eby 33-174 2,265,373 12/1941 Johnson 33--174 2,621,415 12/1952 Cooper 33-175 LEONARD FORMAN, Primary Examiner. 

1. A SURFACE CONTOUR GAUGE FOR USE IN SHAPING LARGE PAROBOLIC ANTENNA REFLECTOR COMPRISING: (A) A RIGID ROTATABLE SUPPORT, (B) A FIRST BEARING AT THE INNER END OF THE SUPPORT ADAPTED TO BE MOUNTED AT THE CENTER OF THE REFLECTOR AND A SECOND BEARING AT THE OUTER END OF THE SUPPORT HAVING LATERALLY ADJUSTABLE MOUNTING MEANS FOR ALIGNING THE SUPPORT FOR ROTATION ABOUT THE PARABOLIC AXIS, (C) A RADIAL ARM ON THE SUPPORT, (D) PARALLEL GAUGING RODS SPACED ALONG THE ARM AND SPRING-URGED INWARDLY IN THE AXIAL DIRECTION, THE LENGTHS THEREOF DECREASING SUBSTANTIALLY PARABOLICALLY WITH RADIAL DISTANCE FROM THE AXIS, (E) AND SUBSTANTIALLY IDENTICAL SETS OF LONGITUDINALLY SPACED MARKINGS ON THE OUTER ENDS OF THE RODS, 